<!doctype html>
<html lang="en">
<head>
	<meta charset="UTF-8">
	<title>Document</title>
	<style type="text/css">
	*{box-sizing:border-box;} 
	#box{width:100%;
		margin:50px;}
	.box{font-size: 40px;
		 color:#fff;
		 background: red;
		text-align: center;
		line-height:100px;
		float: left;
		border:1px solid blue;
		}
	@media screen and (min-width:900px){
		.box{width:16%;	}
	}
	@media screen and (min-width:600px) and (max-width:900px){
		.box{width:30%;	}
	}
	@media screen and (max-width:600px) and (min-width: 0){
		.box{width:45%;	}
	}

	</style>
</head>
<body>
	<div id="box">
		<div class="box">1</div>
		<div class="box">2</div>
		<div class="box">3</div>
		<div class="box">4</div>
		<div class="box">5</div>
		<div class="box">6</div>		
	</div>
</body>
</html>
